<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{margin: 0;padding: 0;}
        #main{height: 100px;display: flex;}
        #main #left{width: 100px;height: 100%; background: red;}
        #main #center{background: blue;flex: 1;height: 100%;}
        #main #right{width: 100px;height: 100%; background: yellow;}
    </style>
</head>
<body>
    <div id="main">
        <div id="left"></div>
        <div id="center">34324</div>
        <div id="right"></div>
    </div>
</body>
</html>